1. Field of the Invention
The present invention relates to a metal V-belt including a metal ring having an endless belt shape and a plurality of metal elements supported by the metal ring in the longitudinal direction of the metal ring. More particularly, the present invention relates to a metal V-belt wherein contact of an innermost periphery of the metal ring with a saddle surface of a metal element, and contact of a protrusion and corresponding concavity of neighboring metal rings is avoided when exiting a driven pulley.
2. Description of the Related Art
Japanese Patent No. 3755833 discloses a driving belt wherein a concavity for receiving a carrier (a metal belt) is provided in a transverse-direction member (a metal element) having a supporting surface and a top portion surface. A point at which the transverse-direction member, while in an inclined state, contacts a supporting surface is called a first contact point and a point at which the transverse-direction member, again while in an inclined state, contacts the top portion surface is called a second contact point, by specifying 0.2<tan− (B/A)<0.8, where A is the distance between the first and second contact points along the axial direction of a driving belt (a metal V-belt) in a position where the transverse-direction member is straight, and B is the distance between the carrier and the second contact point along the radial direction of the driving belt in a position where the transverse-direction member is straight. The disclosed driving belt improves engagement into a drive pulley and a driven pulley by preventing the inclination of a large number of transverse-direction members supported by the carrier.
In the driving belt disclosed by JP '833, the transverse-direction member has sufficient play for positioning itself with respect to the carrier and the pulleys, and the inclination of the transverse-direction member is prevented in order to ensure a good wedge action in the pulleys. However, a play is necessary for inclination between a protrusion and a concavity that engage each other and the play moves the transverse-direction member laterally, with the result that the transverse-direction member and pulleys are apt to come into contact with each other during entry into the pulleys, making it necessary to increase the strength of the transverse-direction member. In addition, because rolling of the transverse-direction member is controlled by the abutment of an outer peripheral surface of the carrier against a top-portion surface (an ear-part bottom surface) of the transverse-direction member, this poses the problem that a specific position of the outer periphery of the carrier that abuts strongly against the top-portion surface is damaged by fatigue, reducing the durability of the whole metal belt.
Japanese Patent No. 3605570 discloses a metal V-belt in which a maximum rolling angle of one metal element relative to upstream-side metal elements is controlled by the engagement between a protrusion and a concavity, wherein the rolling of metal elements is controlled without the metal ring abutting against the metal elements.
The metal V-belt disclosed by JP '570 is intended to solve the problem in the technique disclosed in JP '833. To achieve the intended goal, although rolling of metal elements is controlled without the abutment of a metal ring against the metal elements, a maximum rolling angle of one metal element relative to upstream-side metal elements is controlled by the engagement between a protrusion and a concavity, which requires increasing the strength of the engaging portion.
Japanese Patent Application Laid-open No. 2000-193041 discloses known a metal V-belt having an improved or increased durability that is achieved by setting a clearance between a side surface of a slot of a metal element and a metal ring at a value larger than a clearance in the belt thickness direction between a protrusion and a concavity of the metal element, which prevents the generation of a compressive stress that pinches and bends the metal ring.
In the metal V-belt disclosed by JP '041, the durability of the metal ring is increased by preventing generation of the compressive stress that pinches and bends the metal ring. However, in order to increase the durability of the whole metal belt, it is required to further increase reliability in strength by improving the strength of the metal elements in addition to the strength of the metal ring.